Ganong's Review of Medical Physiology, 23rd Edition

CHAPTER 14

Smell & Taste 225

FIGURE 14–7
Diagram of taste pathways.
Signals from the taste buds travel via different nerves to gustatory areas of the nucleus of the
solitary tract which relays information to the thalamus; the thalamus projects to the gustatory cortex.
(Modified from Kandel ER, Schwartz JH, Jessell TM
[editors]:
Principles of Neural Science,
4th ed. McGraw-Hill, 2000.)

FIGURE 14–8
Signal transduction in taste receptors.
Salt-sensitive taste is mediated by a Na

• -selective channel (ENaC); sour taste is me-
  diated by H


• 
  

  ions permeable to ENaCs; umami taste is mediated by glutamate acting on a metabotropic receptor
  ,
  mGluR4; bitter taste is mediated
  by the T2R family of G protein-coupled receptors; sweet taste may be dependent on the T1R3 family of G protein-coupled receptors which couple
  to the G protein gustducin.
  (Modified from Lindemann B: Receptors and transduction in taste. Nature 2001;413:219.)

  
  

Tongue

Pharynx

Nucleus of

solitary tract

Gustatory

area

Nodose

ganglion

Petrosal

ganglion

N. X

N. IX

N. VII

Geniculate

ganglion

Ventral posterior

medial nucleus of

thalamus

Gustatory cortex

(anterior insula-

frontal operculum)

Chorda

tympani

Glossopharyngeal

N

C CC

NN

CC

NN

CC

X

N

I

O-

α γ

Salty

ENaC, others ENaC, HCN,

others

Taste mGluR4 T2R family,

others

T1R3 (sac locus)

Sour Umami

(L-glutamate)

Bitter Predicted sweet

receptor